1. Field of the Invention
The present invention relates to a data recording apparatus, a data recording method, a data recording and reproducing apparatus, a data recording and reproducing method, a data reproducing apparatus, a data reproducing method, a data record medium, a digital data reproducing apparatus, a digital data reproducing method, a synchronization detecting apparatus, and a synchronization detecting method that are used for recording and/or reproducing a digital video signal and a digital audio signal.
2. Description of the Related Art
A data recording and reproducing apparatus that records a digital video signal and a digital audio signal to a record medium and that reproduces a digital video signal and a digital audio signal therefrom is known. A typical example of such an apparatus is a digital VTR (Video Tape Recorder). In a record processing portion of a digital video signal recording apparatus, digital video data and digital audio data are placed packets with a fixed length. ID information is added to each packet. The packetized data is encoded with an error correction code. A synchronous pattern and ID information are added to packetized data, an error correction code parity, and so forth so as to form a sync block. A plurality of sync blocks are grouped as a sector corresponding to each data type. Each sector as serial data is recorded on a magnetic tape by a rotating head. The length of each sync block in the same sector is the same. The sync blocks are successively assigned unique ID numbers. The ID information has the same value. A product code is used as an error correction code. In other words, a two-dimensional array of data symbols is encoded with an outer code in the vertical direction and an inner code in the horizontal direction. Thus, each symbol is dually encoded. One minimum data encoding/decoding unit of the product code is referred to as ECC block.
On the reproducing side, the start position of each sync block is detected with a synchronous signal. Packets in each sync block are rearranged corresponding to ID numbers and ID information. Since a unique synchronous pattern is added at the start position of each sync block, using the bit sequence of the synchronous pattern, the pattern occurrence interval, successive ID numbers in the same sector, and the same ID information, the phase of a synchronous block can be detected. In other words, when the conditions that the bit sequence of a synchronous pattern matches a fixed pattern, that the same pattern is detected at a position delayed by the block length, and that the block ID is proper are satisfied, the phase of the synchronous block is detected. In the format of such a conventional digital VTR, to easily perform the synchronization detecting process, the length of each synchronous block is fixed (to one type) regardless of the data type.
To record and reproduce video data, a compression encoding process is performed. When video data corresponding to MPEG (Moving Picture Experts Group) standard is compression-compressed, coefficient data generated by DCT (Discrete Cosine Transform) process is encoded with a variable length code. When the amount of data that is recorded per track or every a predetermined number of tracks is fixed, the data amount of the variable length code that is generated in a predetermined time period is limited to a predetermined value. Variable length code encoded data (namely, variable length data) is packed in data areas of a plurality of sync blocks corresponding to a predetermined time period.
The data amount of a digital audio signal is not so large in comparison with that of a digital video signal. To prevent the audio quality from deteriorating in the compressing process and to prevent a complicated process because the data access unit of an MPEG audio signal does not match a video frame and a video signal and an audio signal are switched, non-compressed audio data (linear PCM) is recorded and/or reproduced.
There are as many as 18 types of digital television broadcasting formats in the United States. In such an environment, a digital VTR that can record and reproduce video data in a plurality of formats is desired. When the length of each sync block is fixed to one type regardless of data types as with the conventional digital VTR, although synchronization is easily detected, it is difficult to record data in various formats. Next, this point will be described.
Next, an example of the conventional digital VTR will be described. The VTR records video data and audio data on a tape in a tape format as shown in FIG. 1A. As shown in FIG. 1A, data of six tracks is recorded per frame. One segment is composed of two tracks with different azimuths. In other words, six tracks are composed of three segments. A pair of tracks that compose one segment are assigned track numbers [0] and [1] corresponding to the azimuths. Video sectors are formed on both edges of each track. Video data is recorded on the video sectors. An audio sector is formed between the two video sectors. Audio data is recorded on the audio sector.
In the track format shown in FIG. 1A, audio data of four channels can be handled. Referring to FIG. 1A, A1 to A4 represent sectors of channels 1 to 4 of audio data, respectively. The video data is shuffled (interleaved) and recorded on sectors on the upper side and the lower side. A system area (sys) is formed at a predetermined position of each video sector on the lower side. In FIG. 1A, SAT1 (Tr) and SAT2 (Tm) are areas in which a servo lock signal is recorded. In addition, gaps (Vg1 Sg1, Ag, Sg2, Sg3, and Vg2) with predetermined sizes are formed between individual record areas.
As shown in FIG. 1B, data recorded on the tape is composed of a plurality of blocks that are equally divided (these blocks are referred to as sync blocks). FIG. 1C shows an outlined structure of one sync block. One sync block is composed of an ID (that identifies the current sync block), a DID (that represents the contents of data that follows), a data packet, and an error correction inner code parity. Data is recorded and reproduced as sync blocks (the minimum data recording/reproducing unit is one sync block). For example, a video sector is composed of many sync blocks that are arranged.
One sync block is composed of a synchronous signal, an ID, a data packet, and an inner code parity. Now, one sync block is denoted by
sync block: sync pattern+sync id+data packet+inner parity.
Design condition: The length of one data packet of video data is the same as the length of one data packet of audio data.
Next, as an example of the recording process of video data, the following video data and conditions are considered.
Video data (4:2:2)
Design conditions: Data compression ratio=2 or more (the data amount after data compressing process is 1/2 or less of the data amount before data compressing process).
10 DCT blocks are packed to two sync blocks.
6 tracks per field.
-[525 lines/60 fields] format video signal-
Amount of video data per field:
512xc3x97720xc3x97(8+4+4) bits/8/2=368640 bytes
Number of DCT blocks per field:
512xc3x97720/8/8=5760
10 blocks/2 syncsxe2x86x921152 sync blocks
Length of data packet greater than 368640xc3x97(1/2)/1152=160xe2x80x83xe2x80x83(1)
-[625 lines/60 fields] format video signal-
Amount of video data per field:
608xc3x97720xc3x97(8+4+4) bits /8/2=437760 bytes
Number of DCT blocks per field:
608xc3x97720/8/8=6840
10 blocks/2 syncsxe2x86x921368 sync blocks
Length of data packet greater than 437760xc3x97(1/2)/1368=160xe2x80x83xe2x80x83(2)
An example of the recording process for audio data is as follows:
-Audio data (24 bits, 48 kHz sampled)-
Design condition: Non-compression
AUX data: 6 bytes per field
Number of samples per field in [525/60] format:
48 k/59.94 Hzxc3x9724 bits/8=2402.4 bytes
(5 field sequence)
AUX data of 12 bytesxe2x86x922415 bytes (total data amount)
Number of samples per field in [625/50] format:
48 k/50 Hzxc3x9724 bits/8=2880 bytes
AUX data of 12 bytesxe2x86x922892 bytes (total data amount)
To determine the optimum sync block length of audio data, the products of data packet lengths (162 and 163) and the numbers of sync blocks are obtained as follows.
Now, it is defined that the video compression rate is the ratio of the data amount of video data that has been compressed and the data amount of original video data. The data packet length is selected so that the video compression rate becomes 2 or more. The data packet length of which the excessive record area of audio data in both the [525] format and [625] format is 161. However, since each audio sample is composed of 24 bites (3 bytes), the data packet length should be a multiple of 3. Thus, the data packet length should be 162. Consequently, in the digital VTR format, the data amounts are defined as follows.
[525/60] format video data: 162xc3x971152=186624 bytes
audio data: 162""15=2430 bytes
[625/50] format video data: 162xc3x971368=221616 bytes
audio data: 162xc3x9718=2916 bytes
Error correction outer code parity data is added to each of video data and audio data. The number of outer code parities added to video data is 10% thereof. The number of outer code parities added to audio data is 100% thereof. (In other words, the number of audio symbols is the same as the number of parities.) Since the circuit scale largely depends on the number of parities, the maximum number of parities is limited to 14. In addition, the number of tracks per field is 6. Thus, the sum of the number of data blocks and the number of outer code parities should be divided by 6. In the case of video data, two ECC blocks are formed on one track.
-[525/60] format video data-
1152=(96xc3x972)xc3x976xe2x86x92Number of outer code parities=10
2 ECC blocks per track
Number of data blocks per track+number of outer code parities=(96+10)xc3x972=212
-[625/50] format video data-
1368=(114xc3x972)xc3x976xe2x86x92Number of outer code parities=12
2 ECC blocks per track
Number of data blocks per track+number of outer code parities=(114+10)xc3x972=248
In the case of audio data, one ECC block is formed in one field.
-[525/60] format audio data-
15=(5xc3x973)xe2x86x92Number of outer code parities=5
3 ECC blocks per field
Number of data blocks per track+number of outer code parities=(15+15)/6=5
Number of bytes in unnecessary record area per CH=21 bytes/field
-[625/50] format audio data-
18=(9xc3x972)xe2x86x92Number of outer code parities=9
2 ECC blocks per field
Number of data blocks per track+number of outer code parities=(18+18)/6=6
Number of bytes in unnecessary record area per CH=30 bytes/field
An ID (2 bytes), a block synchronous signal (sync pattern) (2 bytes), and an inner code parity (14 bytes) are added to each data packet and thereby a sync block (180 bytes each) is formed as record data. Thus, video data and audio data are recorded as sync blocks on a tape. The decoder detects the beginning of each sync block with the synchronous signal, corrects an error thereof with an inner code, separates each sync block into a video sync block or an audio sync block with a video/audio data identification flag recorded in the ID, corrects an error of each of a video sync block and an audio sync block with an outer code, and decodes the video sync block and audio sync block to video data and audio data.
Each sync block of video data and each sync block of audio data are structured so that the length of the former is the same as that of the latter. Thus, the beginning of each sync block can be easily detected. FIGS. 2A and 2B show ECC block structures of a conventional digital VTR. FIG. 2C shows the structure of one sync block. FIG. 2A shows the structure of a video ECC block. FIG. 2B shows the structure of an audio ECC block. As shown in FIG. 2C, the length of each video sync block is 180 bytes. The length of each audio sync block is 180 bytes. Thus, the length of each video sync block is the same as the length of each audio sync block. In the [625/50] format and [525/60] format, one video ECC block (FIG. 2A) is structured in such conditions that the number of blocks per frame is 12, that the number of heads is 4, and that the number of tracks per frame is 6. In the [625/50] format, one audio ECC block (FIG. 2B) is structured in such conditions that the number of blocks per frame is 1, that the number of heads is 4, and that the number of tracks per frame is 6. In the [525/60] format, one audio ECC block is structured in such conditions that the number of blocks per frame is 1, that the number of heads is 4, and that the number of tracks per frame is 6.
FIGS. 3 and 4 show the relation between an audio ECC block and audio samples. FIG. 3 shows the arrangement of samples in the case that the field frequency is 50 Hz. FIG. 4 shows the arrangement of samples in the case that the field frequency is 59.94 Hz. In FIGS. 3 and 4, audio sample numbers starts from the beginning of the current field. AUX is system data that represents the contents of audio data. The arrangement of samples and the structure of one ECC block in the [525/60] format (FIG. 3) are different from those in the [625/50] format (FIG. 4). Thus, the audio encoder and the audio decoder each require a circuit that changes a process corresponding to a selected mode.
Next, a multi-rate format will be considered. In the format that the video rate of the conventional VTR format is decreased by 3, in formulas (1) and (2), when xc2xd is substituted with ⅓, the length of each data packet becomes 107. On the other hand, when the length of each audio data packet is the same as the length of each video data packet, since the length of each video data packet should be a multiple of the number of audio samples (3 bytes), the length of each video data packet becomes 108.
The data amount of audio data per field is 2415 bytes in the [525/60] format and 2892 bytes in the [625/50] format. Thus, in the [525/60] format, the data amount of audio data per field becomes 108xc3x973=2484 bytes. In the [625/50] format, the data amount of audio data per field becomes 108xc3x9727=2916 bytes.
Combinations of the data packet length (108=bytes) and the number of sync blocks (the product thereof represents the total data amount) are for example:
Next, the structure of each ECC block will be considered. In the case of video data, two ECC blocks are formed per track.
-[525/60] format video data-
1152=(96xc3x973)xc3x974xe2x86x92Number of outer code parities=10
3 ECC blocks per track
Number of data blocks per track+number of outer code parities=(96+10)xc3x973=318
-[625/50] format video data-
1368=(114xc3x973)xc3x974xe2x86x92Number of outer code parities=12
3 ECC blocks per track
Number of data blocks per track+number of outer code parities=(114+12)xc3x973=378
In the case of audio data, it is assumed that one ECC block is formed in one field. In this case, the number of tracks per field is 4.
-[525/60] format audio data-
23=23xc3x971xe2x86x92Number of outer code parities=23
1 ECC block per field
Number of data blocks per track+Number of outer code parities=(23+23)/4=11.5
-[625/50] format audio data-
27=(9xc3x973)xe2x86x92Number of outer code parities=9
3 ECC blocks per field
Number of data blocks per track+Number of outer code parities=(27+27)/4=13.5
In this case, in the NTSC system, the number of outer code parities is too large. Moreover, in both the cases, the number of blocks per track is not an integer. In other words, an ECC block cannot be formed. Thus, in the [525/60] format, 108xc3x9724=2592 bytes is selected; and in the [625/50] format, 108xc3x9728=3024 bytes is selected.
-[525/60] format audio data-
24=(8xc3x973)xe2x86x92Number of outer code parities=8
3 ECC blocks per field
Number of data blocks per track+Number of outer code parities=(24+24)/4=12
Number of bytes in unnecessary record area per CH=183 bytes/field
-[625/50] format audio data-
28=(7xc3x974)xe2x86x92Number of outer code parities=7
4 ECC blocks per field
Number of data blocks per track+Number of outer code parities=(28+28)/4=14
Number of bytes in unnecessary record area per CH=136 bytes/field
In this example, in the [525/60] format, a loss record area of 138 bytesxc3x974 ch per field (equivalent to 0.35 M bps) takes place. Thus, the record efficiency deteriorates. The loss area is proportional to the number of audio channels.
FIG. 5A shows the structure of a video ECC block whose video rate is changed from 1/2 to 1/3. FIG. 5B shows the structure of an audio ECC block whose audio rate is changed from 1/2 to 1/3. FIG. 5C shows the structure of a sync block in the case that the length of one video sync block is the same as the length of one audio sync block. In the [625/50] format and [525/60] format, one video ECC block (see FIG. 5A) is structured in such conditions that the number of blocks per field is 18, that the number of heads is 4, and that the number of tracks per field is 4. In the [625/50] format, one audio ECC block (see FIG. 5B) is structured in such conditions that the number of blocks per field is 4, that the number of heads is 4, and that the number of tracks per field is 4. In the [525/60] format, one audio ECC block is structured in such conditions that the number of blocks per field is 3, that the number of heads is 4, and that the number of tracks per field is 4.
FIG. 6 shows the relation between an audio ECC block and audio samples. FIG. 6 shows the arrangement of samples with a field frequency of 50 Hz. The arrangement of samples shown in FIG. 6 is largely different from that of original samples shown in FIGS. 3 and 4. The multi-rate type VTR should also record and reproduce the original format data, it should process data of all different arrangements. Thus, the multi-rate type VTR requires signal processing circuits corresponding to all formats of various video data rates and various frame frequencies. Thus, the circuit scale of the multi-rate type VTR becomes large (because of a rise of the IC cost).
Actually, as shown in FIG. 7, 14 formats are considered as combinations of video data rates (25 M bps to 600 M bps), video scan modes (interlace and progressive), and frame frequencies (59.94 Hz, 50 Hz, 29.97 Hz, 25 Hz, and 23.976 Hz). In FIG. 7, an NTSC picture frame is composed of 720xc3x97480 and a PAL picture frame is composed of 720xc3x97576. The interlace mode and progressive mode as video scan modes are denoted by i and p, respectively.
It is necessary to define the lengths of sync blocks for all the formats shown in FIG. 7. The length of each sync block closely relates to the frame frequency, the data amount of video data, the data amount of audio data, and so forth. Thus, when the length of each video sync block is the same as the length of each audio sync block, it is very difficult to select the length (data packet length) that is optimum and common in all the formats. In addition, since the structure of audio data is largely affected by the video rate, circuits corresponding to all video rates should be disposed. If the processes performed by the multi-rate type encoder and decoder are different in the individual formats, the circuit scale becomes huge. Thus, the IC cost rises.
In the conventional digital VTR, one packet of variable length data is placed in one sync block. Thus, in the multi-rate format, the packet rate is proportional to the bit rate. However, since a sync pattern, an ID, and so forth that are added to each sync block have fixed lengths, the size of these data becomes large in the entire size of one sync block. In other words, the redundance of data becomes high.
In addition, since the synchronization detecting circuit of the conventional VTR reproducing system has only one synchronous pattern detecting portion, if input data has a plurality of types of sync blocks with different lengths, the circuit cannot correctly detect a sync pattern.
Therefore, an object of the present invention is to provide a data recording apparatus, a data recording method, a data recording and reproducing apparatus, a data recording and reproducing method, and a data record medium that allow video data and audio data to be recorded and reproduced in a plurality of formats in the structure of which the length of each video sync block is different from the length of each audio sync block.
Another object of the present invention is to provide a data recording apparatus, a data recording method, a data recording and reproducing apparatus, a data recording and reproducing method, and a data record medium that allow a plurality of types of data with different data rates to be recorded and reproduced without an increase of redundancy of data.
A further object of the present invention is to provide a synchronization detecting apparatus, a synchronization detecting method, a digital data reproducing apparatus, and a digital data reproducing method that allow a plurality of types of sync blocks with different lengths to be automatically detected from a reproduced data sequence.
A first aspect of the present invention is a data recording apparatus for recording video data and audio data to a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the apparatus comprising a first error correction code encoding means for separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, a second error correction code encoding means for separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, a means for adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, and a recording means for recording data composed of the first sync blocks and the second sync blocks to the record medium, wherein the length of each of the first sync blocks is different from the length of each of the second sync blocks.
A second aspect of the present invention is a data recording apparatus for recording video data and audio data to a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the apparatus comprising a first error correction code encoding means for separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, a second error correction code encoding means for separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, a means for adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, and a recording means for recording data composed of the first sync blocks and the second sync blocks to the record medium, wherein at least one first data packet is placed in each of the first sync blocks, the number of first data packets placed in each of the first sync blocks being an integer number and depending on the data rate of the video data.
A third aspect of the present invention is a data recording and reproducing apparatus for recording video data and audio data to a record medium and reproducing video data and audio data from a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the apparatus comprising a first error correction code encoding means for separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, a second error correction code encoding means for separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, a means for adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, a recording means for recording data composed of the first sync blocks and the second sync blocks to the record medium, a reproducing means for reproducing data composed of the first sync blocks and the second sync blocks from the record medium, a synchronization detecting means for detecting the synchronous signal from the reproduced data and separating the reproduced data into the first sync blocks and the second sync blocks having different lengths corresponding to the detected synchronous signal, a first error correction code decoding means for decoding data of the separated first sync blocks for each of the first error correction code blocks with an error correction code and generating reproduced video data, and a second error correction code decoding means for decoding data of the separated second sync blocks for each of the second error correction code blocks with an error correction code and generating reproduced audio data, wherein the length of each of the first sync blocks is different from the length of each of the second sync blocks.
A fourth aspect of the present invention is a data recording and reproducing apparatus for recording video data and audio data to a record medium and reproducing video data and audio data from a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the apparatus comprising a first error correction code encoding means for separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, a second error correction code encoding means for separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, a means for adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, a recording means for recording data composed of the first sync blocks and the second sync blocks to the record medium, a reproducing means for reproducing data composed of the first sync blocks and the second sync blocks from the record medium, a synchronization detecting means for detecting the synchronous signal from the reproduced data and separating the reproduced data into the first sync blocks and the second sync blocks having different lengths corresponding to the detected synchronous signal, a first error correction code decoding means for decoding data of the separated first sync blocks for each of the first error correction code blocks with an error correction code and generating reproduced video data, and a second error correction code decoding means for decoding data of the separated second sync blocks for each of the second error correction code blocks with an error correction code and generating reproduced audio data, wherein at least one first data packet is placed in each of the first sync blocks, the number of first data packets placed in each of the first sync blocks being an integer number and depending on the data rate of the video data.
A fifth aspect of the present invention is a data reproducing apparatus for reproducing video data and audio data from a record medium, the video data stored in the record medium being one selected from a plurality of types of data rates, the audio data stored in the record medium being one selected from a plurality of types of data amounts as data edit units, the video data being separated into first data packets, first error correction code blocks being formed with the first data packets, an error correction code encoding process being performed for each of the first error correction code blocks, the audio data being separated into second data packets, second error correction code blocks being formed with the second data packets, an error correction code encoding process being performed for each of the second error correction code blocks, a synchronous signal being added to each of the first data packets and the second data packets and thereby first sync blocks and second sync blocks being formed, the apparatus comprising a reproducing means for reproducing data composed of the first sync blocks and the second sync blocks from the record medium, a synchronization detecting means for detecting the synchronous signal from the reproduced data and separating the reproduced data into the first sync blocks and the second sync blocks corresponding to the detected synchronous signal, a first error correction code decoding means for decoding data of the separated first sync blocks for each of the first error correction code blocks with an error correction code and forming the video data with the decoded first data packets, and a second error correction code decoding means for decoding data of the separated second sync blocks for each of the second error correction code blocks with an error correction code and forming the audio data with the decoded second data packets.
A sixth aspect of the present invention is a data record medium on which video data and audio data are recorded, the video data stored in the record medium being one selected from a plurality of types of data rates, the audio data stored in the record medium being one selected from a plurality of types of data amounts as data edit units, the record medium having a video data record area and an audio data record area, data composed of first sync blocks being recorded in the video data record area, data composed of second sync blocks being recorded in the audio data record area, the length of each of the first sync blocks being different from the length of each of the second sync blocks.
A seventh aspect of the present invention is a data record medium on which video data and audio data are recorded, the video data stored in the record medium being one selected from a plurality of types of data rates, the audio data stored in the record medium being one selected from a plurality of types of data amounts as data edit units, the record medium having a video data record area and an audio data record area, data composed of first sync blocks being recorded in the video data record area, data composed of second sync blocks being recorded in the audio data record area, wherein at least one first data packet is placed in each of the first sync blocks, the number of first data packets placed in each of the first sync blocks being an integer number and depending on the data rate of the video data.
An eighth aspect of the present invention is a data recording method for recording video data and audio data to a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the method comprising the steps of separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, and recording data composed of the first sync blocks and the second sync blocks to the record medium, wherein the length of each of the first sync blocks is different from the length of each of the second sync blocks.
A ninth aspect of the present invention is a data recording method for recording video data and audio data to a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the method comprising the steps of separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, and recording data composed of the first sync blocks and the second sync blocks to the record medium, wherein at least one first data packet is placed in each of the first sync blocks, the number of first data packets placed in each of the first sync blocks being an integer number and depending on the data rate of the video data.
A tenth aspect of the present invention is a data recording and reproducing method for recording video data and audio data to a record medium and reproducing video data and audio data from a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the method comprising the steps of separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second error correction code blocks, adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, recording data composed of the first sync blocks and the second sync blocks to the record medium, reproducing data composed of the first sync blocks and the second sync blocks from the record medium, detecting the synchronous signal from the reproduced data and separating the reproduced data into the first sync blocks and the second sync blocks having different lengths corresponding to the detected synchronous signal, decoding data of the separated first sync blocks for each of the first error correction code blocks with an error correction code and generating reproduced video data, and decoding data of the separated second sync blocks for each of the second error correction code blocks with an error correction code and generating reproduced audio data, wherein the length of each of the first sync blocks is different from the length of each of the second sync blocks.
An eleventh aspect of the present invention is a data recording and reproducing method for recording video data and audio data to a record medium and reproducing video data and audio data from a record medium, the video data having a plurality of types of data rates, the audio data having a plurality of types of data amounts as data edit units, the method comprising the steps of separating the video data into first data packets, forming first error correction code blocks with the first data packets, and performing an error correction code encoding process for each of the first error correction code blocks, separating the audio data into second data packets, forming second error correction code blocks with the second data packets, and performing an error correction code encoding process for each of the second-error correction code blocks, adding a synchronous signal to each of the first data packets and the second data packets and forming first sync blocks and second sync blocks, respectively, recording data composed of the first sync blocks and the second sync blocks to the record medium, reproducing data composed of the first sync blocks and the second sync blocks from the record medium, detecting the synchronous signal from the reproduced data and separating the reproduced data into the first sync blocks and the second sync blocks having different lengths corresponding to the detected synchronous signal, decoding data of the separated first sync blocks for each of the first error correction code blocks with an error correction code and generating reproduced video data, and decoding data of the separated second sync blocks for each of the second error correction code blocks with an error correction code and generating reproduced audio data, wherein at least one first data packet is placed in each of the first sync blocks, the number of first data packets placed in each of the first sync blocks being an integer number and depending on the data rate of the video data.
A twelfth aspect of the present invention is a data reproducing method for reproducing video data and audio data from a record medium, the video data stored in the record medium being one selected from a plurality of types of data rates, the audio data stored in the record medium being one selected from a plurality of types of data amounts as data edit units, the video data being separated into first data packets, first error correction code blocks being formed with the first data packets, an error correction code encoding process being performed for each of the first error correction code blocks, the audio data being separated into second data packets, second error correction code blocks being formed with the second data packets, an error correction code encoding process being performed for each of the second error correction code blocks, a synchronous signal being added to each of the first data packets and the second data packets and thereby first sync blocks and second sync blocks being formed, the method comprising the steps of reproducing data composed of the first sync blocks and the second sync blocks from the record medium, detecting the synchronous signal from the reproduced data and separating the reproduced data into the first sync blocks and the second sync blocks corresponding to the detected synchronous signal, decoding data of the separated first sync blocks for each of the first error correction code blocks with an error correction code and forming the video data with the decoded first data packets, and decoding data of the separated second sync blocks for each of the second error correction code blocks with an error correction code and forming the audio data with the decoded second data packets.
A thirteenth aspect of the present invention is a digital data reproducing apparatus for reproducing data blocks from a record medium, the data blocks having at least two data lengths, the data blocks each having a synchronous pattern for detecting synchronization, comprising a synchronous pattern detecting means for detecting a synchronous pattern of the synchronous signal from the reproduced data, a first memory means for successively storing the reproduced data as data blocks with a predetermined data length and outputting stored data as data blocks with the predetermined data length in the order of order data blocks, the first memory means having a first data length, a first comparing means for determining whether or not both data that is input to the first memory means and data that is output therefrom match the synchronous pattern corresponding to the detected result of the synchronous pattern detecting means, a second memory means for inputting the reproduced data that is the same as the reproduced data that is input to the first memory means, storing the reproduced data as data blocks with the predetermined data length, and outputting stored data as data blocks with the predetermined data length in the order of older data blocks, the second memory means having a second data length K, the second data length K being smaller than the first data length L, the second data length K not being any integer times the first data length L, a second comparing means for determining whether both data that is input to the second memory means and data that is output therefrom match the synchronous pattern corresponding to the detected result of the synchronous pattern detecting means, and an output means for outputting the reproduced data as data blocks with a data length corresponding to the first comparing means or the second comparing means that has detected a match of the synchronous pattern.
A fourteenth aspect of the present invention is a synchronization detecting apparatus for detecting a synchronous pattern from each of data blocks with at least two data lengths, the data blocks each having a synchronous pattern for detecting synchronization, the apparatus comprising a synchronous pattern detecting means for detecting a synchronous pattern from input data, a first memory means for successively storing the input data as data blocks with a predetermined data length and outputting stored data as data blocks with the predetermined data length in the order of order data blocks, the first memory means having a first data length, a first comparing means for determining whether or not both data that is input to the first memory means and data that is output therefrom match the synchronous pattern corresponding to the detected result of the synchronous pattern detecting means, a second memory means for inputting the input data that is the same as the input data of the first memory means, storing the input data as data blocks with the predetermined data length, and outputting stored data as data blocks with the predetermined data length in the order of older data blocks, the second memory means having a second data length K, the second data length K being smaller than the first data length L, the second data length K not being any integer times the first data length L, and a second comparing means for determining whether both data that is input to the second memory means and data that is output therefrom match the synchronous pattern corresponding to the detected result of the synchronous pattern detecting means, wherein when a match of the synchronous pattern is detected in one of the first comparing means and the second comparing means, it is supposed that a synchronous pattern has been detected.
A fifteenth aspect of the present invention is a synchronization detecting method for detecting synchronization of each of data blocks with at least two data lengths, the data blocks each having a synchronous pattern for detecting synchronization, the method comprising the steps of (a) successively storing input data as data blocks with a predetermined data length to a first memory and outputting data as data blocks with the predetermined data length from the first memory in the order of older data blocks, the first memory having a first data length, (b) inputting the input data to a second memory, storing the input data as data blocks with the predetermined data length, and outputting stored data as data blocks with the predetermined data length in the order of older data blocks, the input data being the same as the input data of the first memory, the second memory having a second data length K, the second data length K being smaller than the first data length L, the second data length K not being any integer times the first data length L, (c) detecting a synchronous pattern from the input data, (d) determining whether or not both the data that is input to the first memory and the data that is output therefrom match the synchronous pattern corresponding to the detected result at step (c), and (e) determining whether or not both the data that is input to the second memory and the data that is output therefrom match the synchronous pattern corresponding to the detected result at step (c), wherein when a match of the synchronous pattern is detected at one of step (d) and step (e), it is supposed that the synchronization is detected.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawings.